Signals at different radio frequency (RF) bands are frequently used in various wireless communication applications, such as portable wireless communication devices. Examples of multi-band RF communication technologies include but not limited to CDMA of BC0/1/6, GSM of band 2/3/5/8, WCDMA of band 1/2/4/5/6/8, TD-SCDMA of band 34/39, FDD LTE of band 1/2/3/4/5/7/8/12/13/17/20/25/26, TDD LTE of band 38/39/40/41, GPS, Wi-Fi (2.4 GHz and 5 GHz bands), and others.
Various commonly used multi-band multi-radio system designs are based on multiple discrete components of single-band bandpass filters, duplexers, and switches to handle the multi-band radio operations, such as out-of-band noise and interference, spurious emission, and antenna isolation. Such single-band bandpass filters and duplexer are discrete components and are used to separately filter their corresponding RF signals at different RF carrier frequencies, respectively.